After examining stored drinking water quality in Tanzanian households and finding variability, scientists say this might affect estimates of population level access to safe drinking water, particularly in peri-urban settings.

Dr. Mwifadhi Mrisho, a research scientist at the Ifakara Health Institute, Tanzania and colleagues - Angela Harris, Sean Daly, Amy Pickering, and Michael Harris from the North Carolina State University and Jennifer Davis from the Stanford University, United States – report this in their new publication on the Environmental Science & Technology journal on November 3, 2023.

Their study investigated a total of 193 households in peri-urban Tanzania in their research aimed to assess variability in stored water quality and to characterize uncertainty with different data collection schemes.

Water in 80% of households was poor

Dr. Mrisho and colleagues report that water quality was poor for households, with 80% having highly contaminated water during at least one visit, adding: there was substantial variability of water quality for households, with only 3% of households having the same category (low, medium, or high) of water quality for all five visits. 

“These data suggest a single sample would inaccurately characterize a household’s drinking water quality over the course of a year and lead to misestimates of population level access to safe drinking water,” they report.

How this study was done

Researchers often measure what they call “escherichia coli” in a single-grab sample of stored drinking water and use it to characterize drinking water quality. However, they caution, if water quality exhibits variability temporally, then one-time measurement schemes may be insufficient to adequately characterize the quality of water that people consume. 

“This study used longitudinal data collected from 193 households in peri-urban Tanzania to assess variability in stored water quality and to characterize uncertainty with different data collection schemes. Households were visited 5 times over the course of a year. At each visit, information was collected on water management practices, and a sample of stored drinking water was collected for E. coli enumeration,” the scientists report.

About “escherichia coli”

Escherichia coli is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus escherichia that is commonly found in the lower intestine of warm-blooded organisms. Most of these strains are harmless, but some serotypes are pathogenic and can cause serious food poisoning in their hosts, and are occasionally responsible for food contamination incidents.

>> Learn more about this bacterium here.